Fix freebsd (#324)

See ory/kratos#1645

docker/pkg/system/mknod.go

@@ -1,4 +1,5 @@
 // +build !windows
+// +build !freebsd
 
 package system // import "github.com/ory/dockertest/v3/docker/pkg/system"
 

docker/pkg/system/mknod_freebsd.go

@@ -0,0 +1,22 @@
+// +build freebsd
+
+package system // import "github.com/ory/dockertest/v3/docker/pkg/system"
+
+import (
+	"golang.org/x/sys/unix"
+)
+
+// Mknod creates a filesystem node (file, device special file or named pipe) named path
+// with attributes specified by mode and dev.
+func Mknod(path string, mode uint32, dev int) error {
+	return unix.Mknod(path, mode, uint64(dev))
+}
+
+// Mkdev is used to build the value of linux devices (in /dev/) which specifies major
+// and minor number of the newly created device special file.
+// Linux device nodes are a bit weird due to backwards compat with 16 bit device nodes.
+// They are, from low to high: the lower 8 bits of the minor, then 12 bits of the major,
+// then the top 12 bits of the minor.
+func Mkdev(major int64, minor int64) uint32 {
+	return uint32(unix.Mkdev(uint32(major), uint32(minor)))
+}

docker/pkg/system/mknod_windows.go

@@ -1,3 +1,4 @@
+// +build windows
 package system // import "github.com/ory/dockertest/v3/docker/pkg/system"
 
 // Mknod is not implemented on Windows.